Polymer/surfactant pairs in which the polymer is a polyion and the surfactant is ionic but bears the opposite charge are well known. When the respective charges are of the same sign association between the polymer and surfactant is feeble or absent while with oppositely charged systems the association complex is strong since very strong forces of electrical interaction are involved. A common application of such complexes is the use of cationic polyelectrolytes as flocculants in water purification.
Polysaccharides are hydrophilic carbohydrate polymers of high molecular weight composed of monosaccharide units joined by glycosidic bonds. They are obtained from land or sea sources or by microbiological means and are generally considered to have ten or more monosaccharide units. The units may be of one monosaccharide type but more often are comprised of up to six types of sugar units. They are frequently described from the standpoint of their sources as: phytoglycans, bacterial and fungal polysaccharides, or zoopolysaccharides. Almost half of known polysaccharides are anionic and contain uronic acid residues, though other acid groups such as sulfate phosphate or pyruvate may be present.
Complexes of the abundant anionic polysaccharides are the subject of this application.
Polymer-surfactant interactions have been reviewed by E. D. Goddard in Colloids and Interfaces, 19, 255-329 (1986). It has been shown in several instances that the addition of an "equivalent" amount of charged surfactant to a counter-charged polymer results in a stoichiometric precipitate separating from the aqueous solution. The interaction has been studied by turbidity or change in surface tension or conductance. Although redissolution of the bound complex can occur at low concentration it is unlikely to occur if the charge density of the polymer is very high. It is also highly dependent on the surfactant structure and the complex is generally quite insoluble at higher concentrations. Generally the formation of such precipitates is a "nuisance." We have unexpectedly found the particular fluorochemical complexes described herein are of particular usefulness of virtue of their insolubility and imperviousness to organic liquids.
Kwak and his co-workers cited in Goddard (Ref. 30-37) have shown that the binding affinity of a cation to various polyanions varies considerably with the polyanion: Sodium dextran sulfate&gt;alignate&gt;&gt;pectate&gt;sodium carboxymethylcellulose. Further, the surfactant head group is also important and it was found that the alkylpyridinium group was more tightly bound than alkyltrimethylammonium. Of considerable importance for reasons claimed in this patent, the properties of the charged polymer are substantially changed by the adsorption process.
Studies with a number of surfactants show polymer/surfactant interactions are most favorable (a) the longer the hydrocarbon chain, (b) the straighter the chain, and (c) when the head group is terminal to the chain.
The binding of certain anionic polysaccharides to alkylpyridinium cations is described by A. Malovikova and K. Hayakawa in Structure/Performance Relationships in Surfactants by M. Rosen, ACS Symposium Series 253, American Chemical Society, 1984.
The binding of anionic polysaccharides to perfluoroalkyl containing cations has not been previously described and such complexes form the basis for this invention.
Any polysaccharides containing anionic groups are useful for purposes of this invention.
The use of polysaccharides to extinguish fires has been described in U.S. Pat. Nos. 3,849,315, 3,957,657, 3,957,658, 4,038,195, 4,042,522, 4,060,132, 4,060,489, 4,149,599, 4,306,979, 4,387,032, 4,420,434, 4,424,133, 4,464,267, 4,472,286. Such fire-fighting compositions may also contain fluorochemical surfactants, fluorochemical synergists, hydrocarbon or silicone surfactants, buffers, corrosion inhibitors, chelating agents, antimicrobial agents, solvents, electrolytes, polymeric foam stabilizers, viscosity reducers and pour point depressants.
The fighting of fires on hydrophilic liquids such as methanol, acetone, and the like is more difficult than the fighting of fires on hydrophobic liquids. Aqueous foams are considered the most desirable material for fighting fires on large bodies of such flammable liquids and thixotropic polysaccharide containing compositions are known to form a gelatinous mat above such burning liquids. The mat floats on the burning fuel and protects the foam above it so the fire is rapidly extinguished.
Prior-art compositions describe the use of various types of polysaccharides including heteropolysaccharide 7 described in U.S. Pat. No. 3,915,800 as well as its degraded forms, scleroglucan, mannan gum, xanthan gum, phosphomannon Y-2448, polysaccharide Y-1401, or virtually any water-soluble thixotropic polysaccharide having at least 100 glycose units, or a mol. weight of at least 18,000. Scleroglucan is preferred in U.S. Pat. No. 4,060,132. Locust bean gum, a galoctamannan is also suggested, as is Kelco K8A13, a high molecular weight anionic heteropolysaccharide of formula [C.sub.107 H.sub.158 O.sub.190 K.sub.5 ].sub.n sold by Kelco, San Diego, CA. Suggested too are alginates, alginic and polyglycol esters, pectin, gum arabic, carboxymethyl starch, starch and Actigum CX9 (Ceca S.A., Elf Aquitane, France).
Perfluoroalkyl anion/perfluoroalkyl cation ion-pair complexes have been described in compositions for fighting polar or non-polar solvent fires in U.S. Pat. Nos. 4,472,286 and 4,420,434.
It has now been found that the insoluble polymer complex formed from anionic polysaccharides and perfluoroalkyl cations are much more effective than the polysaccharides used in prior-art fire fighting compositions, will (a) reduce costs due to the use of smaller amounts of fluorochemicals and polysaccharides and (b) will increase the fire-fighting efficiency of such extinguishing agents.